1. Field of the Invention
The present invention relates to a method for making a silicon wafer. In particular, the present invention relates to a method for making a silicon wafer in which the interstitial oxygen concentration of a pulled silicon wafer is calculated on the basis of a light transmission characteristic measured by utilizing parallel polarized light indicated at the Brewster angle into the pulled silicon wafer and a further light transmission characteristic measured by utilizing parallel polarized light incident at the Brewster angle into a floating zone silicon wafer functioning as a reference silicon wafer. The calculated value is then compared with a reference value so as to exclude any pulled silicon wafer having defective interstitial oxygen concentration.
2. Description of Related Art
In the conventional method for making silicon wafers, a pulled silicon wafer is picked up from a production line in order to inspect it. A floating zone type silicon wafer is utilized as a reference wafer since the oxygen concentration of such wafers is known to be negligibly small. The reference silicon wafer is prepared so as to have substantially the same optical behavior as that of the pulled silicon wafer, for example, by mirror polishing and chemically polishing of the front and rear faces thereof, depending on the condition of the pulled silicon wafer when it is picked up. After that, an infrared ray impinges on both the pulled silicon wafer and the reference silicon wafer at the same time to thereby measure a light transmission characteristic of the pulled silicon wafer and the floating zone silicon wafer so that the interstitial oxygen concentration of the pulled silicon wafer is calculated. According to such calculated interstitial oxygen concentration values, it is determined whether or not the pulled silicon wafer is defective.
Such a conventional silicon wafer production method has the following disadvantages because in the conventional method the pulled silicon wafer and the floating zone silicon wafer must have substantially the same optical behavior, e.g., they must both be mirror polished.
(i) A lot of time and complicated measuring operations are required. In particular, the reference silicon wafer must be treated so as to correspond to the picked-up silicon wafer or visa versa.
(ii) It is not possible in practice to inspect all of pulled silicon wafers on a production line.
(iii) Since machining takes place prior to the measurement, detective wafers are unnecessarily machined, thereby reducing efficiency.
(iv) As a result, it is difficult to improve the production efficiency of the production line.